Generally, in a sphygmomanometer, a blood pressure value can correctly be obtained by performing measurement in a state in which a position of a blood pressure measurement site is aligned with a height of a heart. This is because, due to a weight of the blood pressure, the blood pressure value is increased when the measurement site is measured at a position lower than the heart and the blood pressure value is decreased when the measurement site is measured at a position higher than the heart.
Therefore, as illustrated in International Publication WO 2002/039893 (Patent Document 1), there is a wrist type sphygmomanometer that includes angle detection means (angle sensor) to determine whether a measurement posture is proper and notifies whether the measurement posture is proper. In the conventional sphygmomanometer, the measurement is started only when a pressure reference position of the sphygmomanometer falls within the proper range in which the height of the pressure reference position is substantially identical to that of the heart. In this sphygmomanometer, for example, a two-axis angle detection sensor is provided to detect angles in a pitch direction and a roll direction of a front arm, and a difference in height between the position of the measurement site and the position of the heart is calculated based on the detection values of the angles in the two directions.
Patent Document 1: International Publication WO 2002/039893